PostgreSQL: implementing Recursive CTEs and Large Datasets Causing Memory Overruns
I'm building a feature where I've been banging my head against this for hours. I've searched everywhere and can't find a clear answer. I'm currently working with PostgreSQL 14.1, and I've run into a important scenario while trying to use a recursive Common Table Expression (CTE) to traverse a hierarchical dataset. The dataset consists of about 1 million rows, and I'm attempting to get all descendants for a specific parent ID. The CTE runs fine for smaller datasets, but when I scale up, I encounter the behavior: `behavior: out of memory`. Here’s the CTE I'm using: ```sql WITH RECURSIVE descendants AS ( SELECT id, name FROM my_table WHERE parent_id = $1 UNION ALL SELECT m.id, m.name FROM my_table m JOIN descendants d ON m.parent_id = d.id ) SELECT * FROM descendants; ``` I've tried optimizing this by adding an index on the `parent_id` column, which did improve performance slightly, but the memory scenario continues. I also experimented with increasing the `work_mem` setting in my `postgresql.conf`, but it didn't seem to help either. As a temporary workaround, I'm currently batching my queries to limit the number of rows processed at one time, but I’d like to find a more efficient solution to handle the recursion without causing memory overruns. Does anyone have advice on how to optimize a recursive CTE for large datasets, or is there a better approach that avoids this scenario altogether? Any insights would be appreciated! Am I missing something obvious? For context: I'm using Sql on Ubuntu. Any feedback is welcome! Could someone point me to the right documentation?